Command interface systems and methods

ABSTRACT

Apparatus, systems, and methods are disclosed that operate within a memory to execute internal commands, to suspend the execution of commands during a transfer period, and to execute external commands following the transfer period. Additional apparatus, systems, and methods are disclosed.

PRIORITY APPLICATION

This application is a continuation of U.S. application Ser. No.11/840,074, filed Aug. 16, 2007, now U.S. Pat. No. 8,005,995 which isincorporated herein by reference in its entirety.

BACKGROUND

Some electronic devices can operate according to external commandsignals or internal command signals depending on the operating mode. Forexample, an electronic device may operate according to internal commandsignals during a sleep mode, and then switch to operate according toexternal command signals when not in the sleep mode.

When switching modes of operation, there can be a function failure dueto an unexpected command at the boundary of transfer between operationsaccording to external command signals and operations according tointernal command signals. This function failure is also called a commandhazard.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram of a system according to an embodiment of theinvention.

FIG. 2 is a block diagram of a memory device according to an embodimentof the invention.

FIG. 3 is a block diagram of control circuits in a memory deviceaccording to an embodiment of the invention.

FIG. 4 is a block diagram of a logic circuit in a memory deviceaccording to an embodiment of the invention.

FIG. 5 is an electrical schematic diagram of a buffer circuit and amultiplexer in a memory device according to an embodiment of theinvention.

FIG. 6 is an electrical schematic diagram of a buffer circuit and amultiplexer in a memory device according to an embodiment of theinvention.

FIG. 7 is an electrical schematic diagram of a buffer circuit and amultiplexer in a memory device according to an embodiment of theinvention.

FIG. 8 is an electrical schematic diagram of a buffer circuit and amultiplexer in a memory device according to an embodiment of theinvention.

FIG. 9 is a timing chart of a memory device according to an embodimentof the invention.

FIG. 10 is a state transition diagram of states in a sleep mode of amemory device according to an embodiment of the invention.

FIG. 11 is a block diagram of a system according to an embodiment of theinvention.

FIG. 12 is a flow diagram of several methods according to an embodimentof the invention.

DETAILED DESCRIPTION

Digital signals are shown in the Figures and will be included in thefollowing description. A “high” digital signal has a high voltage andmay also be called high, a high signal, or be referred to as being at ahigh level. A “low” digital signal has a low voltage and may also becalled low, a low signal, or be referred to as being at a low level. Insome embodiments, a high digital signal has a higher voltage level thanthat of the low digital signal.

FIG. 1 is a block diagram of a system 50 including a memory device 100and a processor 101 according to an embodiment of the invention. Thememory device 100 includes a control logic circuit 102 coupled toreceive external command signals from the processor 101.

The external command signals include a clock enable signal CKE at a pin106, a clock signal CLK at a pin 108, and a clock signal CLK/ at a pin110. The “/” designation indicates that the signal is active low. A pinis a conductive physical device such as a wire or a metallic terminaland is a specific type of port through which an external signal iscoupled to an electronic device such as the memory device 100. Theactive low clock signal CLK/ is the clock signal CLK inverted. The clockenable signal CKE is a signal instructing validity of the followingclock signal. When the signal CKE is at the high level, the rising edgeof the following clock signal CLK is valid. When the signal CKE is atthe low level, the rising edge of the following clock signal CLK isinvalid. The external command signals also include a chip select signalCS/ at pin 112, a write enable signal WE/ at a pin 114, a column addressstrobe signal CAS/ at a pin 116, a row address strobe signal RAS/ at apin 118, and a data-mask signal DM/ at a pin 120. The external commandsignals at the pins 106-120 are decoded in a command decoder 121.

In addition, the memory device 100 has one or more mode registers 122that are programmed with information for operating the memory device100. The memory device 100 also includes an address bus 124 thatreceives address signals at pins A0-AX, a data bus 126 that receives andtransmits data at pins DQ0-DQX, and a memory circuit 128 that containsdata stored in the memory device 100.

The chip select signal CS/ at the pin 112 is a signal used to select onedevice, such as the memory device 100, out of several devices connectedto the same bus. A low CS/ signal enables the command decoder 121 in thememory device 100, and a high CS/ disables the command decoder 121. Allcommands are masked from the memory device 100 when the CS/ signal ishigh, but READ/WRITE bursts already in progress will continue tocompletion, and a data mask (DQM) operation will retain its DQ maskcapability while CS/ is high. Thus, the low CS/ signal enables a deviceconnected to a bus to respond to commands and data on the bus while thehigh CS/ signal tells the device to ignore the bus. The signal CS/provides for external bank selection on systems with multiple banks.

Address inputs at the pins A0-AX are captured on a falling edge of therow address strobe signal RAS/ at the pin 118, and a row correspondingto the address is opened. The row is held open as long as the rowaddress strobe signal RAS/ is low.

Address inputs are captured on a falling edge of the column addressstrobe signal CAS/ at the pin 116, and a column corresponding to thecaptured address is selected from the currently open row for a read orwrite operation.

The write enable signal WE/ at the pin 114 determines whether a givenfalling edge of the column address strobe signal CAS/ initiates a reador a write operation. A high write enable signal WE/ directs a readoperation, while a low write enable signal WE/ directs a writeoperation. If the write enable signal WE/ is low, data is captured atinput pins on the falling edge of the column address strobe signal CAS/.

The signals WE/, CAS/, RAS/, and CS/ can, in various combinations,represent other commands not described above. For example, a high WE/signal combined with low CKE, CAS/, RAS/, and CS/ signals represent aself-refresh command (SR) and a sleep mode of operation. The CKE signalmay change to high to indicate an end of the SR command (and the sleepmode), and the beginning of an auto-refresh (AR) command. Therefore,high WE/ and CKE signals combined with low CAS/, RAS/, and CS/ signalsrepresent the AR command.

The data-mask signal DM/ at the pin 120 controls input and output overthe data bus 126 during read and write operations. The data bus 126 isactivated to carry data to or from the memory device 100 if thedata-mask signal DM/ is low, and data on the data bus 126 is masked fromthe memory device 100 if the data-mask signal DM/ is high.

The memory circuit 128 is coupled to the address bus 124 to receiveinformation identifying a location for reading data to or writing datafrom the data bus 126. Management of read and write operations isperformed by the control logic circuit 102 upon receiving the externalcommand signals from the processor 101. The read and write operations ofthe memory device 100 are also controlled using a delay lock loop 130having a CLK signal input to adjust timing provided to multiple drivers132. Read and write operations are further controlled with a data strobesignal (DQS) that is generated by a DQS generator 134 coupled to thedrivers 132. The DQS signal is placed on a DQS line 136. In addition,the drivers 132 put data received from the memory circuit 128 through adata buffer 138 on to the data bus 126.

The mode registers 122 have operating information that is programmed bya controller (not shown) on initialization or boot-up of a systemincluding the memory device 100. This information includes a burstlength that determines the maximum number of column locations that canbe accessed for a given read or write command, and a burst type which iseither sequential or interleaved. This information also includes acolumn address strobe signal CAS/ latency that is the number of clockcycles between the registration of a read command by the memory device100 and the availability of the first bit of output data from the memorydevice 100. This information also includes an operating mode that iseither a normal operation mode or a normal operation mode with a resetof the delay lock loop 130.

The memory device 100, as well as the mode registers 122 and theprocessor 101, can each be realized as a single integrated circuit. Thememory device 100 can be formed on a semiconductor die using asubstrate, where the substrate is a material such as silicon, germanium,silicon on sapphire, gallium arsenide, or other semiconductor material.The elements of the memory device 100 are fabricated using conventionalprocessing, well-known to those of ordinary skill in the art, to formthe various circuits within the semiconductor material and for providingelectrical connections for coupling to an address bus, a data bus, andcontrol lines for communication with a controller or a processor.

FIG. 2 is a block diagram of a memory device 200 according to anembodiment of the invention. The memory device 200 may be similar to oridentical to the memory device 100 of FIG. 1. According to someembodiments, the memory device 200 is a synchronous dynamic randomaccess memory (SDRAM).

The processing of external command signals and address signals receivedin buffer circuits in the memory device 200 will now be described.External address signals are received in a buffer 210, external commandsignals RAS/, CAS/, WE/, and CS/ are received in a buffer 216, anexternal clock signal CK is received in a buffer 220, and a clock enablesignal CKE is received in a buffer 226. A reference voltage VREF isreceived in a buffer 230, and a data mask signal DM/ is received in abuffer 234. Data signals DQ are exchanged across a two way buffer 238coupled to a data register 240. The signal DM/ is coupled through thebuffer 234 to the data register 240 to control the movement of data. Aninternal input/output (I/O) bus 242 exchanges data between the dataregister 240 and a number of arrays 246 of memory cells. Each array 246includes a column decoder, a row decoder, and an array of memory cellsto store data—including a parity area of memory cells. Data is alsoexchanged from the internal I/O bus 242 with an error correcting code(ECC) encoder/decoder circuit 250 in a control circuit block 252.

Control circuits in the control circuit block 252 control operations ofthe memory device 200 during a sleep mode of operation. An ECCcontroller 254 and a state machine 258 are also located in the controlcircuit block 252. A power controller 260 exchanges control signals witha plurality of internal voltage generators 262. A temperature sensorcircuit 264 senses a temperature of the memory device 200 and provides asignal indicating the temperature to an oscillator block 270.

The oscillator block 270 generates clock signals that are coupled to thepower controller 260, the ECC controller 254 and the state machine 258.The oscillator block 270 generates an internal clock signal SDCLK thatis coupled to an input of a multiplexer 272, a second input of themultiplexer 272 is coupled to receive the external clock signal CK fromthe buffer 220. The multiplexer 272 generates an internal clock signalICK to clock operations in the memory device 200. The internal clocksignal ICK is derived from the external clock signal CK outside thesleep mode of operation, but is derived from the internal clock signalSDCLK during the sleep mode of operation.

The state machine 258 issues enable signals OscEn to enable theoscillator block 270. The oscillator block 270 generates an internalclock signal ECCLK that is coupled to the ECC controller 254 fordecoding operations.

The external command signals RAS/, CAS/, WE/, and CS/ are coupled fromthe buffer 216 to an input of a multiplexer 274. A second input of themultiplexer 274 is coupled to receive internal command signals generatedby the ECC controller 254. External address signals are coupled from thebuffer 210 to an input of a multiplexer 276, and a second input of themultiplexer 276 is coupled to receive internal address signals from theECC controller 254.

The state machine 258 generates several super low power flag signalsSLPF, SLPFpre, and SLPFpost on lines 280 that are coupled to themultiplexers 272, 274 and 276 to control them during the sleep mode ofoperation. Super is a term of art and does not reflect a particularvoltage level. The signals SLPF, SLPFpre, and SLPFpost are used tocontrol the memory device 200 during the sleep mode of operation, and apotential timing relationship between the signals SLPF, SLPFpre, andSLPFpost will be described below with respect to FIG. 9. The oscillatorblock 270 also generates timing signals that are coupled to the powercontroller 260, the ECC controller 254, and the state machine 258. Aclock enable CKE control circuit 282 is coupled to receive the clockenable signal CKE from the buffer 226, and generates a SR signal toindicate the SR command on a line 284 in response to the clock enablesignal CKE. The SR signal on the line 284 is coupled to the statemachine 258 that generates the signals SLPF, SLPFpre, and SLPFpost basedon the SR signal.

The internal clock signal ICK is coupled from the multiplexer 272 to acommand decoder 286 and an address register 288. The multiplexer 272chooses the source of the internal clock signal ICK based on the signalsSLPF, SLPFpre, and SLPFpost on the lines 280. The multiplexer 274couples command signals to the command decoder 286, selecting either theexternal commands from the buffer 216 or the internal commands from theECC controller 254 based on the signals SLPF, SLPFpre, and SLPFpost onthe lines 280. The multiplexer 276 couples address signals to theaddress register 288, the address signals being either the externaladdress signals from the buffer 210 or the internal address signals fromthe ECC controller 254 based on the signals SLPF, SLPFpre, and SLPFposton the lines 280.

The command decoder 286 generates an auto refresh command (AR) signal onthe line 289 depending on the commands that it receives, and the ARsignal is coupled to the clock enable CKE control circuit 282, a refreshcounter 290, and a multiplexer 292. The signals SLPF, SLPFpre, andSLPFpost on the lines 280 are also coupled to the refresh counter 290,which provides data to the multiplexer 292 that is in turn coupled to arow address latch 294, and a bank control logic circuit 296. Themultiplexer 292 is coupled to receive address signals from the addressregister 288 which are also supplied to a column address latch andcounter 298. The row address latch 294, the bank control logic circuit296, and a column address latch and counter 298 are coupled to providecontrol signals to the arrays 246.

FIG. 3 is a block diagram of control circuits 300 in a memory deviceaccording to an embodiment of the invention. The control circuits 300include a state machine 302 that controls the memory device during asleep mode of operation, similar to the state machine 258 shown in FIG.2.

Others of the control circuits 300 are similar to circuits having thesame name in the memory device 200 shown in FIG. 2. For example, a clockenable CKE control circuit 304 generates a SR entry signal on a line 306and a SR exit signal on a line 308 that are coupled to the state machine302. The SR entry signal and the SR exit signal are also coupled to alogic circuit 310 as is a power-down signal PD on a line 312. The PDsignal indicates a power-down mode of operation for the memory devicewhen direct current (DC) power dissipation is reduced by, for example,disabling input buffers. An ECC controller 316 generates a READY signalon a line 318 that is coupled to the state machine 302, and the statemachine 302 generates an Encode/Decode signal on a line 320 that iscoupled to the ECC controller 316. The READY signal is generated by theECC controller 316 when a decoding operation is complete. The logiccircuit 310 generates control signals as will be described withreference to FIG. 4 below.

A power-off timer circuit 326 generates a T_READY signal on a line 328coupled to the state machine 302, and the state machine 302 generates aTIMER signal on a line 330 that is coupled to the power-off timercircuit 326. The state machine 302 receives a clock signal MSTCLK on aline 340 that is generated by an oscillator block 342. The clock signalMSTCLK is inverted by an inverter 344 to generate a clock signal MSTCLK/on a line 346. The clock signal MSTCLK is a basic clock signal thatcontrols all states implemented by the state machine 302.

The state machine 302 generates a super low power signal SLP on a line350 that is coupled through a first flip flop 352 timed by the clocksignal MSTCLK to generate a SLPF signal on a line 354. The SLP signal onthe line 350 is coupled through a second flip flop 360 timed by theclock signal MSTCLK/ to generate a SLPFpre signal on a line 362. TheSLPFpre signal on the line 362 is coupled through a third flip flop 370that is also timed by the clock signal MSTCLK/ to generate a SLPFpostsignal on a line 372. The signals SLPF, SLPFpre, and SLPFpost are usedto control the memory device during the sleep mode of operation, and atiming relation between the signals SLPF, SLPFpre, and SLPFpost will bedescribed below with respect to FIG. 9.

FIG. 4 is a block diagram of a logic circuit 400 in a memory deviceaccording to an embodiment of the invention. The logic circuit 400 is anembodiment of the logic circuit 310 shown in FIG. 3, and generates avariety of control signals based on the states of signals SLPFpre, SLPF,and SLPFpost.

The signals PD and SR are coupled to inputs of a NOR gate 402 and anoutput of the NOR gate 402 is coupled to an input of an inverter 404 togenerate a control signal EN0/ that is coupled to an input of aninverter 406 to generate a control signal EN0. The signal SR is alsocoupled to an input of an inverter 408 to generate a signal ENCMD thatis coupled to inputs of a NAND gate 410, a NAND gate 412, a NOR gate414, and a NAND gate 416. The signal SLPFpre is coupled to an input ofan inverter 418 to generate an inverted signal SLPFpre/ that is coupledto an input of the NAND gate 410. The signal SLPFpre is also coupled toan input of a NOR gate 420. The signal SLPF is coupled to an input of aninverter 422, a second input of the NOR gate 414, and an input of a NORgate 424. The inverter 422 generates an inverted signal SLPF/ that iscoupled to a second input of the NAND gate 412. An output of the NANDgate 412 generates a control signal EN2/ that is coupled to an input ofan inverter 426 to generate a control signal EN2. The NAND gate 410generates a control signal EN1/ that is coupled to an input of aninverter 428 to generate a control signal EN1. The NOR gate 414generates a control signal EN3/ that is coupled to an input of aninverter 430 to generate a control signal EN3. The signal SLPFpost iscoupled to an input of an inverter 432 to generate an inverted signalSLPFpost/ that is coupled to a second input of the NOR gate 420. The NORgate 420 generates a control signal ECMCS/ that is coupled to an inputof an inverter 434 to generate a control signal ECMCS. The invertedsignal SLPFpost/ is also coupled to a second input of the NAND gate 416,the NAND gate 416 to generate a control signal EN2CS/ that is coupled toan input of an inverter 436 to generate a control signal EN2CS that iscoupled to a second input of the NOR gate 424. The NOR gate 424generates a control signal EN3CS/ that is coupled to an input of aninverter 440 to generate a control signal EN3CS.

The control signals generated by the logic circuit 400 shown in FIG. 4are used to control the buffers and multiplexers in the memory device200 shown in FIG. 2 during the sleep mode of operation.

FIG. 5 is an electrical schematic diagram of a buffer circuit 502 and amultiplexer 504 in a memory device according to an embodiment of theinvention. The buffer circuit 502 and the multiplexer 504 areembodiments of the buffer circuits and multiplexers of the memory device200 shown in FIG. 2.

The buffer circuit 502 and the multiplexer 504 include an arrangement oftransistors that are the same as an arrangement of transistors in buffercircuits and multiplexers shown in FIGS. 6, 7 and 8. These transistorswill be described with respect to FIG. 5; the corresponding transistorsshown in FIGS. 6-8 will be given the same reference numerals and willnot be further described herein for purposes of brevity.

The buffer circuit 502 includes a p-channel transistor 510 having asource coupled to a supply voltage Vdd and a drain. A gate of thep-channel transistor 510 is coupled to receive the signal EN0/ that isalso coupled to a gate of an n-channel transistor 512, the n-channeltransistor 512 having a drain coupled to an output line 514 and a sourcecoupled to a ground voltage reference Vss. The p-channel transistor 510and the n-channel transistor 512 enable the buffer circuit 502 to pass asignal to the multiplexer 504. The drain of the p-channel transistor 510is coupled to a source of a p-channel transistor 520 and to a source ofa p-channel transistor 522 that are coupled in parallel, a drain of thep-channel transistor 520 being coupled to a drain of an n-channeltransistor 530 and a drain of the p-channel transistor 522 being coupledto a drain of an n-channel transistor 532. Sources of the n-channeltransistors 530 and 532 are coupled to the ground voltage reference Vss.A voltage reference Vref is coupled to a gate of the p-channeltransistor 520 and to a gate of the n-channel transistor 532. A gate ofthe n-channel transistor 530 is coupled to the drains of the n-channeltransistors 532 and 512 and the output line 514.

An external signal is coupled to a gate of the p-channel transistor 522such that the buffer circuit 502 generates the external signal on theoutput line 514. In FIG. 5, the buffer circuit 502 receives and thengenerates the external command signal CS/ on the output line 514.

The signal on the output line 514 is coupled to a gate of a p-channeltransistor 540 and a gate of an n-channel transistor 542 in themultiplexer 504. The p-channel transistor 540 and the n-channeltransistor 542 operate as an inverter to invert the signal on the outputline 514 at an output on a line 546 connected to a drain of thep-channel transistor 540 and a drain of the n-channel transistor 542.

Operation of the multiplexer 504 is controlled by several of the controlsignals shown in FIG. 4. The control signal EN2CS/ is coupled to a gateof a p-channel transistor 550 having a source coupled to the supplyvoltage Vdd and a drain coupled to a source of the p-channel transistor540. The control signal EN2CS is coupled to a gate of an n-channeltransistor 552 having a drain coupled to a source of the n-channeltransistor 542 and a source coupled to the ground voltage reference Vss.The control signals EN2CS/ and EN2CS thereby enable the inverter,including the transistors 540 and 542, to pass the signal on the outputline 514 to the line 546 in inverted form. The control signals EN2CS/and EN2CS can also disable the inverter including the transistors 540and 542 such that an internal command signal ECMCS/ can be passed to theline 546 through a pass gate including a p-channel transistor 560 and ann-channel transistor 562. A source of the p-channel transistor 560 iscoupled to a drain of the n-channel transistor 562, and a drain of thep-channel transistor 560 is coupled to a source of the n-channeltransistor 562. A gate of the p-channel transistor 560 is coupled toreceive the signal SLPF/ and a gate of the n-channel transistor 562 iscoupled to receive the signal SLPF such that, during the sleep mode ofoperation, the internal command signal ECMCS/ is coupled through thetransistors 560 and 562 to the line 546. A p-channel transistor 570includes a source coupled to the supply voltage Vdd and a drain coupledto the line 546 and the transistors 560 and 562 to enable thetransistors 560 and 562 to pass the internal command signal ECMCS/ tothe line 546. The p-channel transistor 570 has a gate coupled to thecontrol signal EN3CS. The signal on the line 546 is inverted twice, byfirst and second inverters 580 and 582, and then passed to a commanddecoder.

FIG. 6 is an electrical schematic diagram of a buffer circuit 602 and amultiplexer 604 in a memory device according to an embodiment of theinvention. The buffer circuit 602 and the multiplexer 604 areembodiments of the buffer circuits and multiplexers of the memory device200 shown in FIG. 2.

The buffer circuit 602 represents several buffer circuits that receiveand then generate the external command signals RAS/, CAS/, and WE/ on anoutput line 614. The buffer circuit 602 is enabled by the control signalEN0/. The inverter including the transistors 540 and 542 in themultiplexer 604 is enabled by the control signals EN2/ and EN2, whilethe pass gate including the transistors 560 and 562 is enabled by thecontrol signal EN3 and the signals SLPF/ and SLPF. The multiplexer 604passes on the external command signals RAS/, CAS/, and WE/ to the line646 when the inverter including the transistors 540 and 542 is enabled,and passes corresponding internal command signals ECMRAS/, ECMCAS/, andECMWE/ to the line 646 when the pass gate including the transistors 560and 562 is enabled. The signals on the line 646 are inverted twice, byfirst and second inverters 680 and 682, and then passed to a commanddecoder.

FIG. 7 is an electrical schematic diagram of a buffer circuit 702 and amultiplexer 704 in a memory device according to an embodiment of theinvention. The buffer circuit 702 and the multiplexer 704 areembodiments of the buffer circuits and multiplexers of the memory device200 shown in FIG. 2.

The buffer circuit 702 represents several buffer circuits that receiveand then generate the external address signals A0, A1, A2 . . . BA0,BA1, . . . on an output line 714. The buffer circuit 702 is enabled bythe control signal EN0/. The inverter including the transistors 540 and542 in the multiplexer 704 is enabled by the control signals EN2/ andEN2, while the pass gate including the transistors 560 and 562 isenabled by the control signal EN3 and the signals SLPF/ and SLPF. Themultiplexer 704 passes on the external address signals A0, A1, A2 . . .BA0, BA1, . . . to the line 746 when the inverter including thetransistors 540 and 542 is enabled, and passes corresponding internaladdress signals ECA0, ECA1, ECA2 . . . ECBA0, ECBA1, . . . to the line746 when the pass gate including the transistors 560 and 562 is enabled.The signals on the line 746 are inverted twice, by first and secondinverters 780 and 782, and then passed to a command decoder.

FIG. 8 is an electrical schematic diagram of a buffer circuit 802 and amultiplexer 804 in a memory device according to an embodiment of theinvention. The buffer circuit 802 and the multiplexer 804 areembodiments of the buffer circuits and multiplexers of the memory device200 shown in FIG. 2.

The buffer circuit 802 receives and then generates the external clocksignal CK on an output line 814. The buffer circuit 802 is enabled bythe control signal EN0/. The inverter including the transistors 540 and542 in the multiplexer 804 is enabled by the control signals EN1/ andEN1, while the pass gate including the transistors 560 and 562 isenabled by the signals SLPFpre/ and SLPFpre. The gate of the p-channeltransistor 570 is coupled to the supply voltage Vdd. The multiplexer 804passes on the external clock signal CK to the line 846 when the inverterincluding the transistors 540 and 542 is enabled, and passes acorresponding internal clock signal SDCLK to the line 846 when the passgate including the transistors 560 and 562 is enabled. The signals onthe line 846 are inverted twice by first and second inverters 880 and882 and then are passed to other circuits in the memory device.

The control signals shown and described in FIGS. 5, 6, 7, and 8 aregenerated by the logic circuit 400 shown in FIG. 4 and described above.The corresponding internal command signals and internal address signalsare generated by an ECC controller such as the ECC controller 254 shownin FIG. 2 during a sleep mode of operation. The corresponding internalclock signal SDCLK is generated by an oscillator block such as theoscillator block 270 shown in FIG. 2. The internal command signals arepassed to a command decoder such as the command decoder 286 shown inFIG. 2.

FIG. 9 is a timing chart 900 of a memory device according to anembodiment of the invention. The timing chart 900 includes the signalsSLPFpre, SLPF, and SLPFpost generated by the control circuits 300 shownin FIG. 3 and the state machine 258 shown in FIG. 2, and control signalsgenerated by the logic circuit 400 shown in FIG. 4. The timing chart 900also shows the clock enable signal CKE and external commands received bythe memory device 200 shown in FIG. 2. In particular, the SR command,the AR command, and the SR signal are shown in the timing chart 900. Thesignals are shown with reference to voltage on a vertical axis 902, andwith respect to time on a horizontal axis 904.

As described above, a high WE/ signal combined with low CKE, CAS/, RAS/,and CS/ signals represent the SR command and the beginning of a sleepmode of operation. The SR signal goes high on a rising edge 910following a falling edge of the clock enable signal CKE to begin thesleep mode, and the SR signal goes low on a falling edge 912 following arising edge of the clock enable signal CKE to indicate the end of thesleep mode. The rising edge of the clock enable signal CKE indicates thebeginning of the AR command.

The signal SLPFpre leads the signal SLPF, while the signal SLPFpost lagsthe signal SLPF.

The signals in the timing chart 900 show in particular the activity ofthe internal chip select signal ECMCS/. With reference to FIG. 5, thecontrol signal EN2CS/ disables the inverter while the signal SLPFenables the pass gate in the multiplexer 504 to pass the internal chipselect signal ECMCS/ to the command decoder during the sleep mode ofoperation.

At the end of the sleep mode of operation, designated by the fallingedge 912 of the SR signal, the memory device enters a transfer stateover a transfer period TRANSFER when operation according to internalcommands ends and operation according to external commands begins. Theexternal command AR is received during the transfer period. The internalchip select signal ECMCS/ generated by the ECC controller is high for ashort time between its rising edge 920 and its falling edge 922 and iscoupled to the command decoder to disable the command decoder during thetransfer period. In this way, commands will not be decoded and theexecution of commands will be suspended while the command decoder isdisabled. The possibility of command hazard events are thereforesubstantially reduced, because unexpected commands will not be decodedwhile the command decoder is disabled by the high internal chip selectsignal ECMCS/ during the transfer period.

FIG. 10 is a state transition diagram 1000 of states in a sleep mode ofa memory device according to an embodiment of the invention. Commandsexecuting the transitions in the state transition diagram 1000 aregenerated by a state machine such as the state machine 258 shown in FIG.2.

A decoding state 1006 occurs during system recovery when transitioningfrom battery power. In the decoding state 1006, syndrome patterns arecalculated to detect errors in stored data and, if errors are found, thelocations of the errors are detected and the erroneous data iscorrected.

The state machine shifts to a transfer state 1010 responsive to thecompletion of the decoding state 1006. The transfer state 1010 includesthe operations described with respect to the timing chart 900 of thememory device shown in FIG. 9. The transfer state occurs over a transfertime period bridging operation according to internal commands andoperation according to external commands. The state machine shifts to anidle state 1016 responsive to the completion of the transfer state 1010.During the idle state 1016, the memory device operates according toexternal commands and an external clock signal.

The idle state 1016 ends upon the occurrence of the SR command when CKEis low, and the state machine shifts to an encoding state 1020. The ECCcontroller operates the memory device with internal commands andinternal addresses and the ECC encoder/decoder circuit is controlledsubstantially simultaneously to calculate parity bits during theencoding state 1020. Parity bits or states are calculated and written tothe arrays in the encoding state 1020. The encoding state 1020 can beinterrupted by a high CKE signal in which case the state machine shiftsto the transfer state 1010.

The state machine shifts to a burst refresh state 1040 responsive to thecompletion of the encoding state 1020 and CKE remains low. Data in thearrays is refreshed during the burst refresh state 1040. The statemachine shifts back and forth between the burst refresh state 1040 and apower off state 1060 during the sleep mode when CKE is low. If CKEtransitions to a high signal during either of the burst refresh state1040 or the power off state 1060, the state machine shifts to thedecoding state 1006 described above.

Embodiments of the invention described herein may be implemented withany electronic device that transfers between operation according tointernal commands and operation according to external commands. Thesemiconductor device may comprise a processor or a memory device, suchas an SDRAM memory or Flash memory.

FIG. 11 is a block diagram of a system 1160 according to an embodimentof the invention. The system 1160, in some embodiments, may include aprocessor 1164 coupled to a display 1168 and/or a wireless transceiver1172. The display 1168 may be used to display data, perhaps received bythe wireless transceiver 1172. The system 1160, in some embodiments, mayinclude a memory device such as a dynamic random access memory (DRAM)1174 and/or a Flash memory 1175. The processor 1164 is coupled toexchange data with the DRAM 1174 and the Flash memory 1175. The DRAM1174 may be a synchronous DRAM (SDRAM).

In some embodiments, the system 1160 may include a camera including alens 1176 and an imaging plane 1180 to couple to the processor 1164. Theimaging plane 1180 may be used to receive light captured by the lens1176.

Many variations are possible. For example, in some embodiments, thesystem 1160 may include a cellular telephone receiver 1182 forming apinion of the wireless transceiver 1172. The cellular telephone receiver1182 may also receive data to be processed by the processor 1164, anddisplayed on the display 1168. In some embodiments, the system 1160 mayinclude an audio, video, or multi-media player 1184, including a memorydevice 1185 and a set of media playback controls 1186 to couple to theprocessor 1164. The processor 1164 may also be coupled to exchange datawith an audio device 1192 and/or a modem 1194.

Any of the electronic components of the system 1160 may include circuitsconfigured to transfer between operation according to internal commandsand operation according to external commands according to embodiments ofthe invention described herein. In particular, the processor 1164 issuesexternal commands to be received and processed by components such as theDRAM 1174, the Flash memory 1175, and the memory device 1185. One ormore of the DRAM 1174, the Flash memory 1175, and the memory device 1185include circuits configured to transfer between operation according tointernal commands and operation according to external commands accordingto embodiments of the invention described herein.

Any of the circuits or systems described herein may be referred to as amodule. A module may comprise a circuit and/or firmware according toembodiments of the invention.

FIG. 12 is a flow diagram of several methods 1200 according to anembodiment of the invention. In block 1210, the methods 1200 start.

In block 1220, internal commands are executed with a command decoder ina dynamic random access memory device during a sleep mode of operation,the internal commands being carried by internal command signals.

In block 1230, the sleep mode of operation is ended following a changein external command signals and the execution of internal commands andexternal commands is suspended during a transfer period when an internalactive low chip select signal is high to disable the command decoder.

In block 1240, external commands are executed with the command decoderduring a second mode of operation following the transfer period, theexternal commands being carried by the external command signals. Inblock 1250, the methods 1200 end.

The individual activities of methods 1200 may not have to be performedin the order shown or in any particular order. Some activities may berepeated, and others may occur only once. Embodiments of the inventionmay have more or fewer activities than those shown in FIG. 12.

The novel apparatus and systems of various embodiments may includeand/or be included in electronic circuitry used in high-speed computers,communication and signal processing circuitry, single or multi-processormodules, single or multiple embedded processors, multi-core processors,data switches, and application-specific modules including multilayer,multi-chip modules. Such apparatus and systems may further be includedas sub-components within a variety of electronic systems, such astelevisions, cellular telephones, personal computers (e.g., laptopcomputers, desktop computers, handheld computers, tablet computers,etc.), workstations, radios, video players, audio players (e.g., MP3(Motion Picture Experts Group, Audio Layer 3) players), vehicles,medical devices (e.g., heart monitor, blood pressure monitor, etc.), settop boxes, and others. Some embodiments may include a number of methods,as described above.

The accompanying drawings that form a part hereof show, by way ofillustration and not of limitation, specific embodiments in which thesubject matter may be practiced. The embodiments illustrated aredescribed in sufficient detail to enable those skilled in the art topractice the teachings disclosed herein. Other embodiments may beutilized and derived therefrom, such that structural and logicalsubstitutions and changes may be made without departing from the scopeof this disclosure. This Detailed Description, therefore, is not to betaken in a limiting sense, and the scope of various embodiments isdefined only by the appended claims and the full range of equivalents towhich such claims are entitled.

Such embodiments of the inventive subject matter may be referred toherein individually or collectively by the term “invention” merely forconvenience and without intending to voluntarily limit the scope of thisapplication to any single invention or inventive concept, if more thanone is in fact disclosed. Thus, although specific embodiments have beenillustrated and described herein, any arrangement calculated to achievethe same purpose may be substituted for the specific embodiments shown.This disclosure is intended to cover any and all adaptations orvariations of various embodiments. Combinations of the above embodimentsand other embodiments not specifically described herein will be apparentto those of skill in the art upon reviewing the above description.

The Abstract of the Disclosure is provided to comply with 37 C.F.R.§1.72(b) requiring an abstract that will allow the reader to quicklyascertain the nature of the technical disclosure. It is submitted withthe understanding that it will not be used to interpret or limit thescope or meaning of the claims. In the foregoing Detailed Description,various features are grouped together in a single embodiment for thepurpose of streamlining the disclosure. This method of disclosure is notto be interpreted to require more features than are expressly recited ineach claim. Rather, inventive subject matter may be found in less thanall features of a single disclosed embodiment. Thus the following claimsare hereby incorporated into the Detailed Description, with each claimstanding on its own as a separate embodiment.

What is claimed is:
 1. A method comprising: executing internal commandswith a command decoder in an electronic device during a sleep mode ofoperation of the electronic device; receiving external command signalsin the electronic device to indicate an end of the sleep mode ofoperation; disabling the command decoder with a signal generated by theelectronic device in response to the external command signals during atransfer period between the first sleep mode of operation and a normalmode of operation of the electronic device; and executing externalcommands with the command decoder in the electronic device during thenormal mode of operation of the electronic device following the transferperiod.
 2. The method of claim 1, wherein executing the commands withthe command decoder in the electronic device during the sleep mode ofoperation further comprises: decoding internal command signals intointernal commands in the command decoder in a memory device; andexecuting the internal commands during the sleep mode of operation ofthe memory device.
 3. The method of claim 1, wherein executing externalcommands with the command decoder in the electronic device during thenormal mode of operation further comprises: decoding the externalcommand signals into the external commands in the command decoder in amemory device; and executing the external commands during the normalmode of operation of the memory device.
 4. The method of claim 1,wherein disabling the command decoder includes disabling the commanddecoder when an internal chip select signal operates to disable thecommand decoder in the electronic device.
 5. A method comprising:executing internal commands with a command decoder in an electronicdevice during a sleep mode of operation; generating an internal disablecommand in the electronic device; disabling the command decoder with theinternal disable command during a transfer period between the sleep modeof operation and a normal mode of operation; and executing externalcommands with the command decoder in the electronic device during thenormal mode of operation following the transfer period.
 6. The method ofclaim 5, further comprising generating the internal commands in theelectronic device.
 7. The method of claim 6, wherein executing theinternal commands includes executing the internal commands with thecommand decoder in the electronic device before the transfer period. 8.The method of claim 5, further comprising receiving the externalcommands in the electronic device.
 9. The method of claim 8, whereinexecuting the external commands includes executing the external commandswith the command decoder in the electronic device following the transferperiod.
 10. An apparatus comprising: a command decoder in an electronicdevice to decode and execute internal commands within the electronicdevice during a sleep mode of operation and to decode and executeexternal commands during a normal mode of operation; and a controller inthe electronic device to generate a disable command to disable thecommand decoder during a transfer period between the sleep mode ofoperation and the normal mode of operation.
 11. The apparatus of claim10, wherein the controller is structured to generate the internalcommands executed by the command decoder during the sleep mode ofoperation.
 12. The apparatus of claim 11, wherein the controllercomprises an error correcting code controller circuit to generateinternal command signals during the sleep mode of operation, the commanddecoder to decode the internal command signals into the internalcommands.
 13. The apparatus of claim 10, further comprising a circuit inthe electronic device to generate an internal chip select signal todisable the command decoder during the transfer period.
 14. An apparatuscomprising: an array of memory cells in a memory device; a commanddecoder in the memory device to decode and execute internal commandsduring a sleep mode of operation and to decode and execute externalcommands during a normal mode of operation with respect to the memorycells in the array; and a controller in the memory device, thecontroller structured to generate a disable command to disable thecommand decoder during a transfer period between the sleep mode ofoperation and the normal mode of operation.
 15. The apparatus of claim14, wherein the controller is coupled to the command decoder to generatea chip select signal during the transfer period to disable the commanddecoder.
 16. The apparatus of claim 14, wherein the controller comprisesan error correcting code controller circuit coupled to generate internalcommand signals during the sleep mode of operation.
 17. The apparatus ofclaim 14, further comprising a state machine in the memory device togenerate control signals to control operations of the memory deviceduring the sleep mode of operation.
 18. A method comprising: generatinginternal commands in an electronic device during a sleep mode ofoperation; executing the internal commands with a command decoder in theelectronic device during the sleep mode of operation of the electronicdevice; receiving external commands in the electronic device during anormal mode of operation; executing the external commands with thecommand decoder during the normal mode of operation of the electronicdevice; and disabling the command decoder in the electronic device whenchanging between the sleep mode of operation and the normal mode ofoperation of the electronic device.
 19. The method of claim 18, whereindisabling the command decoder further comprises suspending execution ofthe internal commands in the electronic device between an end of thesleep mode of operation and a beginning of the normal mode of operation.20. The method of claim 19, wherein the electronic device comprises amemory device.